Method of forming bent tubing



Sept. 3, 1946. KEPLER 2,406,838

METHOD OF FORMING BENT TUBING Filed June 28, 1945 2 Sheets-Sheet 1 IN VEN TOR.

Sept. 3, 1946.

F. M. KEPLER METHOD OF FORMING BENT TUBING 2 Sheets-Sheet 2 Filed June 28, 1943 Patented Sept. 3, 1946 UNITED STATES PATENT OFFICE METHOD OF FORMING BE TUBI Francis M. Kepler, Upper Darby;Pa. Application June 28, 1943, Serial No.492, 54'7 The present invention relates to curved pipe or tubing or the like, andit relates more particularly to curved pipe or tubing having uniform inner bore.

An object of the present invention is to provide curved tubing or pipe or the like, which is a more efiicient conductor of fluids due to its uniform inner bore.

Another object of th presentinventionis to provide uniform bore curved tubing or pipe or. the

like, formed with the most economical and ,eflicient use of metal.

Other objects and advantagesof the present invention are apparent in the following detailed description, appended claims and. accompanying give satisfactory and reliable results, although it.

is to be understood that the various instrumentalities of which the invention consists can be variously arranged and organized and that the invention is not limited to the precise arrangements and organizations of the instrumntalities as herein shown and described.

Referring to the'accompanying drawings, in

which like referenc characters indicate like parts throughout:

Figure 1 represents a perspective View ofjone embodiment of the present invention.

Figure 2 represents a cross-sectional view, generally along the line 2-2 of Figure 1;

Figure 3 represents a cross-sectional view, generally along the line 33 of Figure 1.

Figure 4 represents a perspectiv view of the tubing or pipe before it has been bent tothe embodiment of Figure l.

Figure 5 represents a cross-sectional view, of

the pipe shown in Figure 4.

Figure 6 represents a cross-sectional view,

showing the appearance of the tubing or pipe during the process of bending; the appearance of the section during the different stepsfof the process being illustrated.

Figure 7 represents a more or less schematic cross-sectional view of a machine used for bend ing tubing or pipe in accordance with thepresent invention.

Figure 8 represents a frontelevational view of one of the corrugated driving rolls shown in Figure '7.

10 Claims. (Cl. 15354)" Figure 9 represents across-sectional view similar to that of Figure 2, but showing another embodiment of the present invention, in which only the outer periphery of the tubing or pipe is corrugated during the bending operation.

"Figure 10 represents a view generally similar to that of Figure 6, but showing the embodiment of Figure9.

Figure 11 represents a fragmentary perspective View of apiece of pipe, according to my present invention before bending, having but a single thickened-portion, which may be disposed either on the inside of the bend or on the outside of the bend, though-preferably on the outside of the bend."

In my Patent No. 2,310,091, I have described a method of, and apparatus for, bending tubing or pipe by passing the tubing or pipe over a snugly fitting mandrel and between opposed rolls or sheave wheels, one or more of which is or are toothed and power-driven, to form a series of diametrically opposed corrugations along the sides of the tubing, and then passing the socorrugated tubing over a curved mandrel and between opposed rolls or sheaves to-bend the tubing; the corrugations alon the inner periphery of the bent tubing'becoming deeper and closer together accordion-wise, and the corrugations along the outer periphery of" the bent tubing becomin shallower and farther apart, accordionw1se.

In my Patent No, 2,310,091, I employed tubing or pipe having a uniform wall thickness. Since, during the bending operation, the inner and outer peripheries of the tubing assume alternately greater and smaller thickness than the original wall thickness, it isnecessary, when employing tubing with such uniform wall thickness, to start with tubing which has oversized walls so that the corrugationavill not reduce the thickness below the minimum basic factor required in the pipe. Since the thickness of the uncorrugated portions of the, tubing is not affected during the bending operation, the use of uniform walled tubing is somewhat wasteful of metal since the uncor rugated portions of the final bent tubing are thicker-walled than is necessary.

According to my invention, I employ tubing or pipe which is thickeralongthe portions to be corrugatedthan at the other portions which are not to be corrugated so that, during the bending operation, the thickness of the corrugated portion' is kept above the minimum basic factor, while the thickness of the uncorrugated portion is no greaterthan is required, In this way, no

more metal is used than is absolutely necessary to meet the safety and strength requirements of the final bent tubing.

A machine suitable for performing the corrugating and bending operations of the present invention is described in my Patent No. 2,310,091 and the means for accomplishing these steps will be described herein only schematically; having in mind the details of construction of the machine of my Patent 2,310,091.

I may provide a central power-driven driving roll or sheave wheel 20 having transversely-extending corrugating teeth 2| formed along the semi-circular groove extending about its outermost periphery as shown in Figures 7 and 8.

A second power roll or sheave wheel 22 similar to the roll 20 and having corrugating teeth 23 similar to the teeth 2| of the roll 20 is disposed in juxtaposition to the roll 20; the semi-circular outer grooves of the rolls 20 and 22 defining a generally circular opening therebetween.

The roll 22 may be rotated at the same rate of periphery of the bend, as compared with the inner periphery thereof. This may also be accomplished by increasing the diameter of the driving roll 22. If roll 22 is of a suitably larger diameter than roll 20, to allow for the difference between the inside and outside of the bend, then the two rolls, with reference to each other, could rotate at the same rate of speed.

A plurality (as for Example 3) of additional uncorrugated grooved rolls or sheave wheels 24 are also disposed about the central drive roll 20, as shown in Figure '7. The rolls 24 may either be idle rolls or power-driven rolls. If powerdriven, the rolls 24 may rotate either at the same speed as the rolls 20 and 22, or, if large-diameteredpipe is to be bent, at a slightly. greater speed. The rolls 24 which are adapted to contact the outer periphery of the bent tubing, rotate in the same direction as the roll 22. That is. in Figure 7 for example, each of rolls 24 rotates clockwise.

A mandrel 25 having a circular cross-section and having a semi-circular portion 26 and a straight portion 21, is positioned about the center driving roll 20; its cross-section being the same as the inner bore of the tubing and somewhat less than the openings defined between the roll 20 and the rolls 22 and 24, so that an annular clearance is provided between the mandrel 25 and the adjacent pairs of rolls. A reduced stem 28 extends upwardly from the straight portion 21 of the mandrel 25.

The mandrel 25 is held in position intermediate the rolls by any suitable supporting means (not shown), as, for instance the supporting means shown in my Patent 2,310,091. This supporting means may not be required when the machine is in operation; the mandrel being held in position by the tubing being, bent under the pressure of the driving and bending rolls, so that it may be considered as a free floating mandrel.

In carrying out the present invention, a straight length of tubing 29, as shown in Figures 4 and 5, is provided. The length of tubing 29 drel 25.

may be of steel or other suitable metal and may be either seamless or Welded tubing or pipe. The length of tubing 29 has a generally cylindrical inner periphery, but has one, or a pair of diametrically opposed raised shoulders 30 formed on its outer periphery. Thus, it can be seen in Figures 4 and 5, that the thickness of the wall of the tubing 29 at the top and bottom thereof is less than the thickness at the sides thereof. That is, the wall thickness at the top and bottom is the minimum thickness required for the final tubing, while the side thickness required for the final tubing is initially greater than that required.

While the length of tubing 29, as shown in Figures 4 and 5, corresponds generally to that required to make a bend, it is to be understood that longer or shorter lengths of tubing canbe treated in the manner to be described hereinbelow, and that the final bent product can be cut on: into any desired lengths.

In practicing -the present invention, the straight length of tubing 29 is first placed over the reduced stem 28 of the mandrel 25, and moved downward upon the uppermost straight portion 2'! of the mandrel 25.

Power is then applied to the driving rolls 29 and 22 to cause the rolls to rotate downwardly at the opening defined therebetween. The corrugating teeth 2| of the roll 20 and the teeth 23 of the roll 22 catch the raised shoulders 30 of the tubing 29 and force the tubing downwardly upon the mandrel 25.

Since the mandrel fits snugly Within the inner bore of the tubing 29, it is held in position within the tubing under pressure of the rolls 20 and 22, and may be considered as a floating mandrel.

The tubing 29 is thus forced through the annular clearance between the mandrel 25 and the opposed corrugating teeth 2| and 23 of the driving rolls 20 and 22.

This annular clearance is such that the metal of the shoulders 30 of the tubing 29 is displaced by the corrugating teeth 2| and 23 to form alternate crests 3| and troughs 32, as shown in Figure 6.

Since the straight portion 27 of the mandrel 25 fits more or less snugly within the inner bore of the tubing 29, the inner wall of the tubing remains smooth and generally unaltered in passing through the annular clearance intermediate the driving rolls 20 and 22.

As the tubing 29 is forced further down upon the curved portion 26 of the mandrel 25 by the driving rolls 20 and 22, it is bent more or less smoothly along its axis into the curvature of the semi-circular portion 26; the bent tubing being forced along between the roll 20 and the uncorrugated rolls 24, finally to emerge in the form shown in Figures 1 to 3.

During the bending operation the crests 3! and troughs 32 (which were originally the same on both sides of the tubing 29) becom altered in shape. That is, the crests and troughs along the inner shoulder of the tubing become compressed accordion-fashion to become closer together and deeper as at 3|a and 32-a in Figure 6. The crests and troughs on the outer side of the tubing 29, on the other hand, become extended accordion-fashion, to become shallower and farther apart, as shown at 3|-b and 32-1), in Figure 6.

The inner wall of the tubing 29 remains smooth due to the close fitting portion 26 of the man- It can be seen that this corrugating and bending reduces the Wall thickness at points along the shoulders 3|] of the tubing 29, especially along the inner shoulder. The original thickness of the shoulders 30 is so proportioned that the minimum thicknessof the inner shoulder of the final bent tubing is approximately the same as the thickness of the top and bottom portions of the tubing.

One of the two thickened portions or shoulders 30 (that is, if a pair of such shoulders are used instead of merely a single shoulder) is preferably made of somewhat different circumferential extent than the other, and, preferably the shoulder which is to be disposed on the inside of the bend, is made of a lesser circum ferential extent than the shoulder which is to be disposed on the outside of the bend. The reason for this is that on the outside of the bend, the material is stretched while on the inside of the bend, the tendency is to compress or contract the wall, and also because on the outside of the bend, the corrugations made by the rolls become shallower, while on the inside of the bend, the corrugations remain deeper.

Another embodiment of the present invention is shown in Figures 9 and 10. In this embodiment, the tubing is corrugated only along the shoulder extending alongthe outer peripheryof the bend; the inner shoulder being left uncorrugated. This is done by simply omitting the corrugating teeth from the inner driving roll 20.

In this embodiment of the present invention, one of the two shoulders '30 on the pipe may be eliminated entirely, as indicated in Figure 11, so that the pipe or tubing, prior to any bending, will have only a single so-called shoulder 30 or thickened-portion 30. Indeed,I may dispose the single shoulder 30 either on the inside of the bend or on the outside'of the bend, and I may provide teeth only upon the corresponding roll 22 or 29, according to whether I place the single shoulder 30 on the outside or on the inside of the bend, respectively. Thus, I may drive the pipe through the bending operation by a single corrugated roll 22 or 25!, on the outside or on the inside of the bend, respectively; the other roll, in each instance, then serving only as a backing roll to give support, and such backing roll (whether it be the outside roll 22 or the inner roll 2i!) may or may not be powerdriven, that is, it may either be power-driven or may be idle.

The bent tubing of the present invention has a smooth and uniform inner wall surface so that a minimum of turbulence and resistance is created during the passage of fluids therethrough. Furthermore, the present invention makes it possible to bend tubing without changing its inside characteristics or dimensions, so that it can be connected (by Welding orother means) to a straight piece of tubing having similar inside dimensions. This provides a pipe line which is substantially uniform throughout its entire length regardless of bends. Thus, no constrictions or irregularities are presented in the path of fluid flow, so that friction is greatly decreased and power loss during fluid transmission is minimized.

As stated hereinabove, the novel design of the tubing of the present invention employs a minimum of metal in providing bent tubing having the advantages set forth hereinabove.

The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof, and it is therefore desired that the present embodiments bore against distortion, and bending said tubing to deepen the corrugations along one of said shoulders on the inner side or the bend and to flatten the corrugations along the otherof said shoulders along the outer side of the bend, while supporting said inner bore against distortion, thereby to provide bent tubing having a generally smooth and uniform inner bore and having minimum wall thickness not substantially less than that of the original straight tubing.

2, A method of forming bent tubing which comprises forming a generally straight length of tubing having a uniform inner bore and having integral raised shoulders extending along thesides thereof, forming diametrically opposed series of peripherally extending corrugations along said shoulders while suporting said inner bore against distortion, and bending said tubing to deepen the corrugations along one of said shoulders on the inner side of the bend and to flatten the corrugations along the other of said shoulders along the outer side of the bend, while supporting said inner bore against distortion, to give a minimum wall thickness of the corrugated shoulders substantially the same as the Wall thickness at the top and bottom of the bend and notsubstantially less than that of the original straight tubing.

i 3. A methodof forming bent tubing which comprises forming a generally straight length or tubing having a generally cylindrical inner bore and having an outer integral raised shoulder formed on a side thereof, forming a series of peripherally extending corrugations alongsaid shoulder while supporting said inner boreagainst distortion, and progressively bending said tubing while supporting said inner bore against distortion, said corrugations adjusting themselves accordion-wise 'dur ing the bending operation to accommodate the ensuing displacement of metal, thereby to provide bent tubing having a generally smooth and uni-' form inner bore and having minimum wall thickness not substantially less than that of the original straight tubing.

4. A method of forming bent tubing which comprises forming a generally straight length of tubing having a generally cylindrical inner bore, forming a'series of peripherallyextending corrugation along one side of said tubing while supporting said inner bore against distortion, the top, bottom and other side of said tubing being left uncorrugated, and progressively bending said tubing so that the corrugations extend along the outer side of the bend while supporting said inner bore against distortion, said corrugations being spread apart accordion-wise during the bending operation to accommodate the ensuing displacement of metal, thereby to provide bent tubing having a generally smooth and uniform inner bore and having minimum wall thickness not substantially less than that of the original straight tubing.

5. A method of forming bent metal tubing which comprises forming a generally straight length of tubing having a generally cylindrical inner bore and having outer integral raised shoulders extending along the sides thereof, passing the tub ing over a smooth snugly-fitting mandrel and through the opening defined by a pair of juxtaposed driving rolls, each having an annular transversely corrugated channel formed in its outer periphery, thereby to form diametrically opposed series of peripherally extending corrugations on said shoulders while supporting said inner bore against distortion, and thereafter passing the socorrugated tubing over a curved mandrel between a pair of juxtaposed channeled bending rolls thereby to deepen the corrugations along the inside of the bend accordion-wise and to flatten the corrugations along the outside of the bend accordion-wise to accommodate the ensuing displacement of metal, while supporting said inner bore against distortion, thereby to provide bent tubing having a generally smooth and uniform inner bore and having minimum wall thickness not substantially less than that of the original straight tubing.

6. A method of forming bent metal tubing which comprises forming a general straight length of tubing having a generally cylindrical inner bore and having an outer integral raised shoulder extending along a side thereof, passing the tubing over a smooth snugly-fitting mandrel and through the opening defined by a pair of juxtaposed channeled driving rolls, one of said rolls having a series of transverse corrugations formed along its channel, thereby to form a series of peripherally extending corrugations along said shoulder While supporting said inner bore against distortion, and thereafter passing the so-corrugated tubing over a smooth snugly-fitting curved mandrel between a pair of juxtaposed channeled bending rolls, with the corrugations extending along a side of the bend, said corrugations adjusting themselves accordion-wise during the bending operation to accommodate the ensuing displacement of metal, said inner bore being supported against distortion during said bending, thereby to provide bent tubing having a generaly smooth and uniform inner bore and having minimum wall thickness not substantially less than that of the original straight tubing.

'7 A method of forming bent metal tubing which comprises forming a general straight length of tubing having a generally cylindrical inner bore and having an outer integral raised shoulder extending along a side thereof, passing the tubing over a smooth snugly-fitting mandrel and through the opening defined by a pair of juxtaposed channeled driving rolls, one of said rolls having a series of transverse corrugations formed along its channel, thereby to form a series of peripherally extending corrugations along said shoulder while supporting aid inner bore against distortion, and thereafter passing the so-corrugated tubing over a smooth snugly-fitting curved mandrel between a pair of juxtaposed channeled bending rolls, with the corrugations extending along a side of the bend, said corrugations adjusting themselves accordion-wise during the bending operation to accommodate the ensuing displacement of metal, said inner bore being supported against distortion during aid bending, the minimum wall thickness along th curved corrugated shoulder being substantially the same as the wall thickness at the top and bottom of the bend and not substantially less than that of the original straight tubing.

8, A method of forming bent metal tubing which comprises forming a general straight length of tubing having a generally cylindrical inner bore and having an outer integral raised shoulder extending along a side thereof, passing the tubing over a smooth snugly-fitting mandrel and through the opening defined by a pair of juxtaposed channeled driving rolls, one of said rolls having a series of transverse corrugations formed along its channel, thereby to form a series of peripherally extending corrugations along said shoulder while supporting said inner bore against distortion, and thereafter passing the so-corrugated tubing over a curved mandrel between a pair of juxtaposed channeled bending rolls with the corrugations extending along the outside of the bend, thereby to flatten the corrugations accordion-wise to accommodate the ensuing displacement of metal, while supporting said inner bore against distortion, thereby to provide bent tubing having a generally smooth and. uniform inner bore and having minimum wall thickness not substantially less than that of the original straight tubing.

9. A method of forming bent tubing which comprises forming a generally straight length of tubr ing having a uniform inner bore and having a single integral raised shoulder extending along one side thereof, forming a series of peripherallyextending corrugations along said shoulder while supporting said inner bore against distortion, and bending said tubing with said shoulder extending along the outer side of bend while supporting said inner bore against distortion, thereby to flatten the corrugations on the shoulder and to provide bent tubing having a smooth and uniform inner bore and having minimum wall thickness not substantially less than that of th original straight tubing.

10. A method of forming bent tubing which comprises forming a generally straight length of tubing having a uniform inner bore and having integral raised shoulders extending along the sides thereof, one of said shoulders having a larger circumferential dimension than the other, forming diametrically opposed series of peripherally-extending corrugations along said shoulders while supporting said inner bore against distortion, and bending said tubing with the larger shoulder extending along the outer side of the bend and the smaller shoulder extending along the inner side of the bend while supporting said inner bore against distortion, thereby to deepen the corrugations along the inner shoulder and to flatten the corrugations along the outer shoulder and to provid bent tubing having a smooth and uniform inner bore and having minimum wall thickness not substantially less than that of the original straight tubing.

FRANCIS M. KEPLER. 

